Grote 46003 clearance light gaskets!!

I understand your issues. Seems like a total waste to have to replace the light just for a gasket, but that seems to be the throw away society. Any auto supply store should have a fair supply of various gasket material that can be cut as you need. If you need rubber, have you thought of an inner tube? Available at farm suppliers, auto supply shops or even bicycle shops. You'll have to do a bit of cutting, but....? As to the rivets, how about just drilling out the rivets and replacing them with stainless screws? You might have to put in some plastic/nylon sheetrock anchors or other expanding type anchors (Molly fasteners) if the holes in the caps are bigger than the largest screw that will fit the lamp.